The present invention is generally related to fuel-fired heating appliances, and more specifically to the control of a variable speed blower motor in a variable heating fuel-fired appliance.
Many fuel-fired appliances that provide variable heating rates utilize a variable speed motor to drive a blower fan for establishing air flow for combustion. Manufacturers of such heating appliances typically utilized an ignition control module to control the ignition operation of the appliance, and a separate motor processor module to control the variable speed blower motor. These prior art systems relied on the ignition control module to send a high or low speed signal, or alternatively a pulse-width modulated signal to the motor processor, which accordingly had to be configured to interpret the signal and establish the desired speed. The ignition controls of these prior art systems typically had no feedback from the motor processor, and relied on a pressure switch to determine if the desired blower flow rate had been established. If the blower speed was not sufficient to close the pressure switch, the ignition control could only request an incremental increase in speed without any feedback from the motor processor. HVAC systems accordingly relied on two separate controllers for system operation, in which an ignition processor could not verify whether the motor processor had received a speed request signal or whether the motor controller was even functioning.